1. Technical Field
The present invention relates to an electroluminescent device and a method for preparing the same and, more particularly, to an electroluminescent device which can achieve emission of polarized light without reforming materials used to form organic layers by including a metal nano pattern having a grating period which enables emission of polarized light, and a method for preparing the same.
2. Description of the Related Art
An electroluminescent device, specifically, an organic electroluminescent device (organic EL device) is a self-emissive display that emits light by recombination of electrons and holes in a fluorescent or phosphorescent organic layer when a current is applied to the organic layer. Organic ELs are lightweight, have simple constituent elements, are easily fabricated, and have superior image quality and a wide viewing angle. In addition, organic EL devices have electrical properties suitable for portable electronic equipment, such as complete creation of moving pictures, high color purity, low power consumption, low voltage driving, and so forth. The organic electroluminescent device can be used in applications in a wide variety of fields, such as display devices, backlight units and the like.
Particularly, research efforts directed at achieving polarized electroluminescence are actively being conducted.
U.S. Pat. No. 6,777,531 B2 discloses polyfluorene, end-capped with at least one charge-transporting moiety, as a material forming an emission layer in an organic electroluminescent device, and devices having the same. In this patent, it is taught that a material for an alignment layer is directly rubbed to achieve polarized electroluminescence.
U.S. Pat. No. 6,649,283 B2 discloses layers comprising polyimide and organic functional material such as hole transport material, electron transport material and/or emitter material, the layers being prepared by mixing the functional material with a polyimide precursor material, forming a thin film out of the mixture, and converting said mixture into doped polyimide. The referenced patent describes a method of obtaining polarized emission which includes rubbing a polyimide-based material and aligning a polymeric liquid crystalline material on the rubbed polyimide-based material.
U.S. Pat. Nos. 6,579,564 B2 and 6,489,044 B1 disclose a layer coated with a friction transferred alignment material so as to have alignment properties, and a device comprising the same. According to these patents, polarized emission is achieved by preparing an alignment layer deposited by a friction transfer method and coating an electroluminescent layer on the alignment layer.
In the conventional electroluminescent devices proposed in the patents discussed above, in order for the proposed devices to emit polarized light, organic layer forming materials need to be converted. However, organic layers are derived from numerous kinds of materials. Thus, it is quite a big challenge to convert such organic layer forming materials into emissive materials. Accordingly, there is a need for development of electroluminescent devices enabling emission of polarized light without reforming the materials used to form organic layers.